The present invention generally relates to semiconductor devices and more particularly to a fabrication method of semiconductor device that uses an anisotropic etching process and a semiconductor device fabricated by such a fabrication process.
Conventionally, polysilicon gate electrode of semiconductor devices is formed by an anisotropic dry etching process of a polysilicon film by using an RIE process.
With such an anisotropic dry etching process, Si atoms ejected from the polysilicon film with the etching process cause reaction with the etching gas to form a byproduct, and such a byproduct protects the sidewall surface of the gate electrode pattern from further etching as they are deposited on such a sidewall surface. As a result, the polysilicon gate electrode is formed in the state that it is defined by a pair of straight sidewall surfaces perpendicular to the substrate surface.
Further, such an anisotropic etching process has been used also for formation of STI (shallow trench isolation) structures that include a device isolation trench.